1. Field of the Invention
The present invention relates to a process control system for controlling, for example, a complex process type semiconductor wafer processing apparatus, and a method for transferring process data for the process control system.
2. Discussion of the Background
Recently a substrate processing apparatus such as a semiconductor wafer processing apparatus and a liquid crystal panel processing apparatus has remarkably tended to be automated and robotized in accordance with an improvement in performance of microcomputers. For example, various types of complex process type processing apparatuses have been developed, in which the chambers of respective processes are coupled to each other by means of a transfer unit or a robot thereby to automate a process from transfer of wafers or the like to reception thereof into the apparatus. In such an apparatus, various conditions (temperature, concentration, pressure, time, etc.) in a process are monitored by different sensors provided in each of the process chambers, and data of the monitored conditions (process data) is transferred and accumulated in a host computer. If the process data is made visible by a monitor and detected automatically, the optimum process conditions of mass-production line are set and controlled.
As the number of chambers synthesized with the semiconductor wafer processing apparatus and liquid crystal panel processing apparatus is increased, the control load of a controller (hereinafter referred to as a main controller) for unifying a group of machine controllers for separately controlling the chambers is increased more and more. The main controller transfers the process data to the host computer at the request of the host computer. The amount of process data to be transferred to the host computer increases in accordance with the number of process chambers and accordingly the control load tends to increase.
If, under the above circumstances, a process data transmission request is generated from the host computer during the execution of a process and both the process control and process data transfer control occur on the time basis at the same time, the control load of the main controller is greatly increased and the timing of the process control is delayed, with the result that it is likely that the whole process control will be made unstable.